Every game you'll find a new rock that contains some hidden bells. You can smack the rock with a shovel to knock some bells out of it. Repeated hits during a limited time period will earn you additional bells, but normally the number is limited somewhat by the step you automatically tack back after whacking the rock. A great trick is to stand against a rock, then dig holes to your left and right, as well as behind you. Now when you hit the rock, it won't send you flying backward. This lets you whack it more frequently to produce more bells before the invisible timer expires, increasing your total earnings.